The present invention relates to pintle-type valves; more particularly to pintle valves for permitting the controlled admission of exhaust gases into the fuel intake manifold of an internal combustion engine; and most particularly to a slidable pintle shield for preventing entrance of corrosive gases and moisture into the valve actuator.
It is well known in the automotive art to provide a variable valve connecting the exhaust manifold with the intake manifold of an internal combustion engine to permit selective and controlled recirculation of a portion of an engine""s exhaust gas into the fuel intake stream. Such recirculation is beneficial for reducing the burn temperature of the fuel mix in the engine to reduce formation of nitrogen and sulfur oxides which are significant components of smog. Such a valve is known in the art as an exhaust gas recirculation (EGR) valve.
Typically, an EGR valve has a valve body enclosing a chamber disposed between a first port in the exhaust manifold and a second port in the intake manifold; a valve seat dividing the chamber between the two ports; a valve pintle having a valve head fitted to the valve seat and a valve stem extending from the valve head through a bearing mounted in a third port in a sidewall of the valve body; a spring-retained bearing splash shield; and a solenoid actuator mounted on the exterior of the valve body and operationally connected to the outer end of the valve pintle.
A problem inherent to EGR valve applications is that the managed fluid (exhaust gas) is moisture-laden, corrosive, and dirty. If this gas is allowed to enter the actuator by leaking along the valve pintle, then internal corrosion, malfunction, and ultimate failure of the actuator can result. Such failure can lead to emission non-compliance and can incur significant cost to a vehicle manufacturer if a recall is required.
Two known solutions to this problem are a sealed, impermeable actuator, or, alternatively, an actuator having working components which are unaffected by exhaust gas. Either of such actuators is currently impractical for cost and performance reasons. Further, a sealed actuator would be even more vulnerable to damage from trapped moisture if a leak should develop in the seal; and a corrosion-resistant actuator would require materials of construction which are less magnetically efficient than the currently used soft iron and powder metals, thus dictating a substantially larger solenoid.
What is needed is a device which may be fitted to an EGR valve and actuator that significantly reduces or eliminates gas and moisture intrusion into the actuator without impairing efficiency, size, and performance of the valve and actuator. Preferably, such a device is simple and inexpensive to fabricate and install.
The present invention is directed to a novel shield for a pintle valve, such as an exhaust gas recirculation valve for an internal combustion engine, for mitigating leakage or gas and moisture along valve pintle into the actuator to prevent corrosion and failure of the actuator. The shield is a tubular member having an equatorial radial flange and is slidably mounted on the pintle in an annular chamber between the valve body and the actuator. The inner diameter of the tube is selected to be as close-fitting to the pintle as possible while still being slidable thereupon to be adapted to either of two operating positions. During engine shutdowns, the shield is drawn by gravity toward the valve body to form a seal with the flange against the bearing splash shield, preventing or minimizing the escape of moist, hot gases under low pressure from the valve along the pintle. Such gases may be present at elevated temperatures after a running engine is shut down and are known to destructively permeate the actuator. During engine running, exhaust gases being managed within the valve may be under substantial pressure and therefore may be forced along the pintle through the bearing bore and bearing splash shield toward the actuator. In response, the shield may be forced by the gases slidably upwards on the pintle to form a seal with the flange against the actuator, allowing the leaked gases to escape radially from the pintle without invading the actuator.